This study investigates the impact of organization structure on corporate demand for reinsurance. Previous research has shown that the unique corporate groupings in Japan known as the “keiretsu” have relatively low bankruptcy costs, low agency conflicts, low information asymmetry, and low effective taxes. These conditions should mitigate the benefits of reinsurance purchase. This conjecture is tested by examining demand for reinsurance of Japanese non‐life insurance companies during 1974–2010. Consistent with the prediction, keiretsu non‐life insurers have lower reinsurance purchase than independent non‐life insurance companies. The effects of the keiretsu structure also receded when keiretsu groupings' power was weakened after the asset bubble burst and the breakdown of the convoy system in mid 1990s. Consistent with previous studies, Japanese mutual insurers also purchase more reinsurance than stock insurers.